An electronic component unit is incorporated in an electronic apparatus such as a server computer. The electronic component unit includes a large-scale integrated circuit (LSI) chip package mounted on a substrate of a system board. A heat sink is received on the LSI chip package. Four bolts are utilized to couple the heat sink to the substrate of the system board, for example. The bolts penetrate the base plate of the heat sink and the substrate of the system board. The tip ends of the bolts are screwed into a bolster plate overlaid on the backside of the substrate. A coil spring is interposed between the head of each bolt and the base plate. The coil spring exhibits an elastic force forcing the head of the bolt to be distanced from the base plate. The base plate is thus urged against the LSI chip package.
A predetermined urging force is ensured for keeping a reliable contact between the base plate of the heat sink and the LSI chip package. The bolt is screwed into the bolster plate to fix the heat sink on the substrate of the system board. A tool such as a torque driver is utilized to screw the bolt into the bolster plate. The urging force is adjusted based on the amount how much the bolt is screwed into the bolster plate. For example, it is required to attach/detach the bolt for the maintenance work at a spot where the server computer has been placed. The attachment/detachment of the bolt with a tool is time consuming.    [Patent Document 1] Japanese Laid-open Patent Publication No. 2004-71665    [Patent Document 2] Japanese Laid-open Patent Publication No. 10-4175